Magnetic Resonance Imaging (MRI) is an advanced technique for visualizing internal human anatomy and disease processes. Its primary use has been for disease diagnosis where its utility in differentiating soft tissue anatomy offers unique visualization characteristics compared to other methods (i.e. CT x-ray, plain X-ray, PET scanning, etc). Recently, the advantages of this unique visualization capability have begun to be applied for targeting and guiding diagnostic biopsies and focal therapies. Because MRI requires a very powerful magnetic field and precise measurements of the molecular movements created by an electromagnetic (radio-frequency) pulse, any distortions that may occur from nearby electrically conductive or magnetic materials will degrade the resulting image data. Therefore, special non-magnetic and non-conductive tools and equipment have been developed by necessity for use in these types of minimally invasive procedures. This set of devices so far includes some surgical instruments, needles, anesthesia equipment, some robotic type devices that use pneumatic powered controls, and the like.
However, many tools and devices that are common to other interventional medical procedures are not available or have yet to be developed for use during MRI. In particular, one such device that is a manually operated mechanical arm for holding a full spectrum of medical devices. The utility of this type of device for holding and positioning medical instruments, guidance devices and other support implements that can remain in a constant spatial relationship to the patient is basic to many invasive medical procedures. The engineering challenges for such a device are not trivial because of the functional requirements that must be met. These include safety and non-interference with the MRI machine, ease of use, sterility, stability, strength, and small axial dimensions because of the very limited space within most MRI scanners. As a consequence, even though there is currently both a need and demand for such a device, nothing that approaches the ideal of meeting these functional requirements has been available until the present invention.
In our copending United States Published Application 2006/0016006 A1, filed Jan. 26, 2006, which is assigned to the same assignee as the subject invention and whose disclosure is incorporated by reference herein there is disclosed and claimed a system is for supporting a patient during computed axial tomography imaging. The system includes a movable platform formed of a radiolucent material, a discrete attachment region in the platform, and a curvilinear articulating arm coupled to the platform at the discrete attachment region. The free end of the arm is arranged to hold any desired medical device, e.g., a clamp, a bracket, or a linear instrument such as a biopsy needle guide, etc. Such devices can be collectively referred to hereinafter as “effectors” (with each particular device being referred to as an “effector”). The patent application also discloses a method for supporting a patient during a plurality of procedures. The method includes: disposing the patient on a movable platform formed of a radiolucent material; positioning a device with respect to the patient, the device being disposed on a curvilinear articulating arm coupled to the platform; placing the platform, positioned device, and patient in a computed axial tomography imaging system and performing an imaging procedure. The curvilinear articulating arm basically includes a central arm having a ball-sleeve arrangement that forms joints to enable the arm to move with six degrees of freedom so that it can be bent into any desired curvilinear shape. To that end, the central arm includes a plurality of sleeves with spherical balls disposed therebetween forming ball and socket connections. In the preferred exemplary embodiment, three balls of a first size are disposed adjacent one another proximate one end of arm, while the remaining balls are of a second size smaller than the first size. Sleeves of a first size and sleeves of a second size smaller than the first size are provided for accommodating the balls of the first size and the second size, respectively, while a transition sleeve is provided, as are intermediate sleeves. The sleeves are configured and dimensioned to receive the balls at ends thereof and thus permit articulating of sleeves with respect to each other. A metal tensioning wire runs generally centrally through sleeves and balls to hold the arm in the shape that it is bent into. One exemplary operation of a wire tensioning mechanism is shown and described in U.S. Pat. No. 3,858,578 (Milo), which is expressly incorporated herein by reference thereto.
In our Provisional Patent Application Ser. No. 60/892,343, filed on Mar. 1, 2007, entitled Device For Positioning Instruments At A Magnetic Resonance Imaging Scanner, which is assigned to the same assignee as this invention and whose disclosure is incorporated herein, there is disclosed and claimed a device for holding an end effector, e.g., a biopsy needle, a clamp, etc., at an MRI apparatus. The device comprises an articulating arm having a proximal end portion, a free distal end portion and a flexible elongated tensioning member located within the arm between the proximal end portion and the distal end portion. The proximal end portion of the arm is in the form of a base arranged to mount the device on or at the MRI apparatus. The free distal end portion of the arm is arranged to mount a desired item thereon (e.g., clamp, a bracket, a biopsy needle guide, etc.). The arm has a longitudinal axis and includes plural segments of non-magnetic and non-conductive material or any material that is magnetic resonance and/or artifact-free. The segments of the arm are arranged to be moved with respect to one another, but are restricted from twisting about the longitudinal axis to enable the arm to be moved into a desired shape and held in that shape when the elongated tensioning member is tensioned.
In accordance with one preferred aspect of the invention of that Provisional Application at least one of the segments is adapted to pivot about a first pivot axis that is perpendicular to the longitudinal axis of the arm and at least one of the segments that is/are immediately adjacent the at least one of the segments is adapted to pivot about a second pivot axis that is perpendicular to the longitudinal axis. The first and second axes are perpendicular to each other. This arrangement precludes the tensioning member from twisting when the arm is moved or bent into its desired orientation.
In accordance with another preferred aspect of the invention of that Provisional Application the tensioning member (e.g., a ribbon like arrangement consisting of an array of plural side-by-side sections or runs of a cord) is mounted within the arm and is actuatable to enable the tension in the elongated tensioning member to be established to hold the arm in the desired shape and to enable the tension in the elongated tensioning member to be released, whereupon the shape of the arm can be changed.
While the holding devices of the prior art may be generally suitable for their intended purposes, they still leave something to be desired from various standpoints. The device of the subject invention addresses those needs.